Low-dose penicillin taken late in pregnancy and in early life increased aggression, impaired social behavior and anxiety-like behavior, increased inflammation in the brain, and led to permanent changes in the gut microbiome in mice. Concurrent supplementation with the probiotic, Lactobacillus rhamnosus JB-1, prevented some of these alterations. βeta-lactam antibiotics are the most frequently prescribed drugs given to infants and children. Several clinical studies have shown an association between early life antibiotic use and an increased risk of developing allergies, inflammatory bowel diseases, obesity, and poorer neurocognitive outcomes later in life.